There are lots of ways to stay on a budget. Clipping coupons and waiting for sales are good ways to stretch your dollar, but let's face it: Gas will likely never go on sale. While some stations offer gas coupons or promotions, they're usually too small to really make a dent in anyone's driving budget. If gas stations aren't going to put gas on sale, you'll have to.

No, that doesn't mean you need to start selling gas at a discount. But by modifying some of your driving habits, you can increase your fuel efficiency and use less gas, bringing the cost down. So how much can you save? With the simple green driving tips we've compiled here, you could increase your fuel economy (and savings) by up to 47 percent. And if you want to decrease your fuel consumption ev­en mo­re, you can make some of the lifestyle changes that we've also listed.

The other benefit of cutting back on gas? It's better for the environment. Better fuel economy means less pollution emitted by cars and less dependence on foreign sources of oil. That's why these driving tips are doubly green: green for the planet and green in your wallet. Find out more on the next page.

Green Driving Tip 10: The Junk in Your Trunk

­Your car burns gas for energy. It's food for the engine, which­ is what makes the car run. The more work the car has to do, the more energy it needs. It's sort o­f like how a marathoner needs to eat a lot more than a couch potato (though couch potatoes may beg to differ). This principle is already pretty clear to most people. It's why large SUVs have worse gas mileage than small cars. The added weight of the SUV makes the car work harder.­

No matter what kind of car you drive, eliminating weight can go a long way toward increasing your car's fuel efficiency. Now, before you take a chainsaw to the bumper, there are probably less drastic steps you can take. Have a ski or bike rack on your car? Unless you're on your way to a ski trip or bike ride, take it off. That unused rack adds weight and wind resistance. And if you're like most people, you probably have some junk in your trunk. Clean it out. Sports equipment, strollers, gym bags and rock salt left over from winter driving are all hurting your fuel economy. The EPA estimates that for every extra 100 pounds your car caries, it loses 2 percent in fuel economy, so just by cleaning up your act, you can start on the road to saving [source: fueleconomy.gov].

Read on to find tips that can increase your car's fuel economy by a lot more than 2 percent.

Green Driving Tip 9: Your Wallet is Riding on Your Tires

The weight your car is carrying around isn't the only thing that can affect your fuel economy. Your tires can, too. Proper tire maintenance is an often overlooked way to increase your fuel economy. The easiest way to use your tires to save money is to make sure they're properly inflated. Tires that are underinflated negatively affect fuel efficiency. Imagine trying to ­roll a bean bag up a hill. It would take a lot of energy because it droops all over everything. In contrast, it's easy to roll a well-inflated ball up a hill. Like a ball, properly inflated tires have less contact with the road, which means they encounter less friction, so the engine doesn't have to work as hard to move the car.

To find out how much air should be in your tires, check your owners' manual, or the inside of the driver's door (where the latch is). Most cars have a sticker there that explains the optimal amount of air for the tires. The Environmental Protection Agency (EPA) estimates that properly inflating your tires can increase fuel efficiency by 3 percent [source: fueleconomy.gov].

If you want to get even more efficient, you can switch from regular tires to low rolling resistance tires. Low rolling resistance tires are harder than regular tires, so they encounter even less friction. Treehugger.com reports that using low rolling resistance tires can lead to a 6 percent increase in fuel economy [source: Treehugger.com]. There are some downsides to the tires, however. They're a lot harder than regular tires, so your car's ride and handling may suffer. Also, don't run out and buy low rolling resistance tires unless you were planning on replacing your tires anyway. The savings in fuel won't offset the cost of new tires. Wait until you need new tires before getting them. Finally, work with your mechanic or tire shop to find the proper low rolling resistance tires for your car.

Now that you've cleaned out your car and checked the tires, it's time to hit the road. Read on to find out how you can change the way you drive to save gas.

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Green Driving Tip 8: Limit Your Need for Speed

One of the best ways to improve your fuel economy is to change the way you drive. Speeding, accelerating and braking hard can deplete efficiency by 33 percent, according to the Environmental Protection Agency (EPA) [source: fueleconomy.gov]. Why? When you stop, start or accelerate, your car has to overcome inertia. Inertia is the resistance an object has to a change in its state of motion. In order to get moving, or to stop, a car has to overcome inertia. You've probably heard that objects in motion tend to stay in motion, and objects that are stopped tend to stay stopped. That's because of inertia.

Overcoming inertia requires energy. When you're talking cars and energy, you're talking gas. You can use less energy to overcome inertia if you do it slowly. What would make you more tired: pulling a heavy wagon slowly from a stop to an all-out run, or pulling the same wagon immediately to a sprint? Pulling the wagon slowly lets you build momentum to help overcome inertia, using less energy. In your car, you should accelerate slowly from stops, allowing the car's momentum to help it accelerate.

Once the car is in motion, you should try to preserve that momentum by avoiding situations where it can be lost. Say you're driving down the road and see a light up ahead turn from yellow to red. Rather than keep your foot on the gas and brake at the last second, you should take your foot off the gas and slowly approach the light. Not only will coasting save gas, but you might not even have to come to a full stop before the light turns green again, meaning that your car will have to overcome much less inertia to get going.

The speed at which you drive on the highway, where stopping and starting aren't likely to be a problem, also impacts your fuel efficiency. The EPA says that most cars run at maximum efficiency at 60 miles per hour, and every five mph over 60 decreases efficiency by 6 percent. So on your next road trip, slow down. You'll make up the time by not having to stop for gas as often.

Next time you're driving around and smell some delicious fried food, don't look for a restaurant as the source. Some alternative fuels are going green, but smell golden brown. Read on to find out more.

Hypermilers

There's green driving, and then there's really green driving. Hypermilers are people who strive for incredible feats of fuel economy by changing the way they drive. By modifying how they stop, start and cruise on the highway, some are even able to get 75 miles per gallon.

Green Driving Tip 7: Want fries with that alternative fuel?

Alternative fuels like biodiesel are often inexpensive (or even free).

Most people exercise to burn off fat, which is excess energy stored on the body. With obesity rates in the U.S. rising, one thing we have plenty of is fat, and it turns out you can run your car on it.

Now, before you hook up your car to your hips, it's not that simple. Alternative fuels, like biodiesel, allow an engine to run off of natural, renewable fuel sources like plant or animal oils. These oils, like peanut or vegetable oil, or even leftover french fry grease, have to undergo some processing to turn their fat into energy an engine can use, but once they do, they can power a regular diesel engine. One side effect is that as the car runs, it will smell like whatever type of oil was used to power it. Biodiesel cars can give you a mean french fry craving that way.

Biodiesel has the benefit of being largely free or low-cost (if you have access to large quantities of grease or cooking oil) and renewable, since plant oils can be replenished by growing more plants and animal oils are a by-product of food production. There are downsides, though. There isn't as much energy in these oils as there is in petroleum-based oils like gasoline or diesel, so mileage is lower. Also, there isn't a biodiesel infrastructure in place. If you want this kind of fuel, you'll often have to make it yourself. There are kits that help you do it, but it's a lot of work.

A second and more practical gas alternative is ethanol. Ethanol is fuel made from plant material like corn or wood pulp. It's essentially alcohol with a little bit of gasoline mixed in. Not every car engine can run on ethanol. General Motors has several models it designates as flex fuel capable. That is, those models can run either on gasoline or ethanol. Ethanol is also becoming available at a number of gas stations across the country, making it more practical than biodiesel.

Since ethanol is made from plants, it's a renewable resource. It can also be produced in the U.S., which protects the economy from global forces. There are a number of downsides to ethanol, however. It takes a lot of energy to produce. Because it picks up impurities when it travels by pipe, ethanol must be transported by truck and barge -- which is expensive. Finally, so many farmers have sold their crops to ethanol producers that it has contributed to the rise of food prices across the world.­

Like gasoline, there are downsides to using ethanol as fuel. But while a large-scale switch to ethanol may not be ideal, ethanol is one way individual drivers can go green and be a part of the overall solution to conserving resources and easing pollution.

Green Driving Tip 6: Time to trade in for a more efficient car?

If you're really serious about driving greener, you can get a more fuel-efficient car. Like switching from a large SUV like the Chevrolet Tahoe, which has an EPA-estimated combined gas mileage of 16 mpg, to a small car like the Honda Fit, which has an EPA-estimated combined gas mileage of 30 mpg.

You can also go much greener and consider getting a gas-electric hybrid car. The Toyota Prius has an EPA-estimated combined gas mileage of 46 mpg. That means switching from the Tahoe to the Prius could save you nearly six gallons of gas per week. The Prius' gas mileage is so high because its gasoline engine can be shut off at low speeds or in stop and go traffic. In those situations, the car is powered by an electric motor, which means no gas is used and no pollutants are emitted.

Not ready to buy a new car? How about sharing the car you have? Keep reading to learn about the green benefits of car pooling.

Green Driving Tip 5: Car Pooling

By car pooling, a group of Tokyo businessmen get to save gas and enjoy each others' company.

If you really want to cut down on your fuel usage, car pooling is a great way to do it. When two (or more) people buddy up and ride together, the number of cars on the road drops and gas is saved. It's that simple.

A number of cities and towns have car pooling resources. Some heavily congested areas use High Occupancy Vehicle (HOV) lanes to encourage carpooling. HOV lanes are lanes set aside for cars that carry a certain number of people. Get in the lane with fewer people in your car, and you'll get a ticket. Since most people drive by themselves, HOV lanes have fewer cars and less traffic. Car poolers benefit by saving time, while the cities they're in benefit by having fewer cars on the road and less pollution.

Ride sharing is another car pooling resource many areas have. Ride sharing is a formal program that matches interested car poolers together. That can be a big help, since you may not live near anyone you work with. Ride sharing programs also sometimes provide central locations for picking up and dropping off car poolers, so time isn't spent driving to all the participants' houses. Some programs also provide help if car pooling plans fall through. For example, if the person you rode into work with gets sick and leaves early (or if you get sick and have to leave early), a ride sharing program will make sure you get home.

Car pooling isn't just a good way to drive green and break up a lonely commute; it's a good way to save a lot of money. By alternating driving days with another driver, you'll cut your gas costs by half. And by not driving your car as much, you'll save on routine maintenance. Driving only half as much will also slow the rate you put miles on your car, helping its resale value.

Want to spend even less time on the road and less money on owning a car? Keep reading to learn about the benefits of car sharing.

Green Driving Tip 4: (Car) Sharing is Caring

Car sharing is another way to drive green that's gaining in popularity, especially in urban areas. People who may not drive every day but still want a car to run errands or drive on weekends benefit most from car sharing. Car sharing is usually run by a service like Zipcar, though there are nonprofit and informal car sharing services. Members pay a monthly fee and have access to an entire fleet of cars when they need one. The cars are parked in designated spots around the city, so members only need to make a reservation, and then go to the designated pickup spot.

Car sharing has major environmental benefits because it lessens the number of cars on the road. Members don't drive just because they have a car. They plan trips, and if they don't need a car, they don't use one. Still, a car is available to them if they need to make a big trip to the grocery store, pick someone up at the airport or if they want to go to the beach for the day. Members also benefit by having access to a car without any of the headaches of ownership. They usually don't have to pay for gas, insurance or maintenance, and the monthly membership fee is less than a typical car payment. So if you really want to go green but aren't ready to totally give up a car yet, car sharing may be the way to go.

If you still need to get around, but want to go even greener than sharing a car, share a bus! On the next page, you'll learn about the green benefits of mass transit.

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Green Driving Tip 3: Another One Rides the Bus

Public transport, like the D.C. Metro, cuts back on pollution and congestion.

Whether you own a car, use a car sharing service, or don't drive at all, mass transit is a great way to get around while staying green. If two people car pooling removes one car from the road, the benefits are even greater when 30 people ride a bus and eliminate all their cars from the streets. The benefits really add up when you think of the hundreds of people on one train. Not only does mass transit ease congestion, it reduces pollution. It also encourages green development by promoting greater population density around subway stations and major bus lines.

There's also an economic benefit to the riders. Take a typical commuter in the Washington D.C. area. Commuting from suburb to suburb, he or she spends roughly $35 a week on gas, plus an additional $12.50 a week on tolls (not to mention wear and tear on the car). That works out to about $9.50 a day in commuting costs. The local Metro Bus costs only $1 a ride, which means he or she would save $5.50 a day, or $27.50 a week. Plus, the metro bus can use HOV lanes, allowing a commuter to save traffic frustration and glide by, relaxing with a book. The benefits are even greater for workers who have to pay for parking. Look into mass transit options in your area to see how much you could save.

Want to save even more? Go green by going to work less. It's not laziness. Staying home can help the environment.

Even Greener: Alternative Fuel Mass Transit

What's greener than people riding a bus? People riding a green bus! A number of mass transit systems are trying out alternative fuel buses, including hybrids, buses powered by natural gas, and buses powered by biodiesel. Having buses run on alternative fuels really increases the benefits of mass transit because not only does it reduce the number of cars using gas, it reduces the need for gas, period.

Green Driving Tip 2: The Four-day Workweek

It's likely that most of your time driving is spent going to and from work. One way to ease congestion, pollution and the amount of gas you use is to go to work only four days a week. We're not advocating skipping. The four-day workweek is a movement that's growing so much that some state governments are considering it for their workers.

In a four-day workweek, instead of working eight hours a day, five days a week, you work ten hours a day, four days a week. The time at work and the amount of work you get done stays the same, but with one day less at the office, your commuting costs and pollution go down 20 percent. Companies could save money by having four-day weeks, too -- their energy bills would be lower because their electricity consumption would be less. Marion County, Fl., switched its workers to a four-day week and expects to save $250,000 this year on energy costs alone [source: KING5.com]. The state of West Virginia is also considering making the switch for its workers.

What's even better than an extra day of not commuting? How about not commuting at all? Read on to see how telecommuting may be the best green driving tip there is.

Negotiating a Four-day Workweek

So you want to go down to four days a week? How do you get your boss to agree? Before you even talk to your boss, come up with a plan that shows how a four-day week will benefit the company. Talk to your human resources department to see if your company offers flexible schedules. Be prepared to have a trial period. Finally, make sure your productivity doesn't drop off, and be willing to put in 10-hour days when you're at work.

Green Driving Tip 1: Telecommuting

Think of all the gas (and time) you could save by telecommuting, or working from home.

If taking one day off from commuting per week is a good thing, taking five days off is even better. Telecommuting, or working from home, is growing in popularity. While not every job advocates telecommuting (you probably wouldn't want your dentist to do it), many workers can do their jobs with just a computer and a high-speed Internet connection.

There are a number of different approaches to working from home. Some workers do it full-time, while others do it a few days a week per month. It's easy to think of telecommuters goofing off at home in their pajamas while everyone else is hard at work, but a number of companies have found that telecommuters actually are more productive than office workers because they have fewer interruptions and less stress [source: The TeleWork Coalition].­

­The savings of telecommuting are potentially huge. Even if people who are able to telecommute did so less than two days a week, 1.35 billion gallons of fuel could be could be saved [source: Green Car Congress]. The potential savings to businesses is great too: They would have lower energy costs and happier workers and have to supply less office space. Best of all, because less energy would be used powering offices and less gas would be used commuting, the environmental benefits would be enormous. The benefits of telecommuting show that the best green driving tip is not to drive at all.

To learn more about hybrids, biodiesel and telecommuting, accelerate slowly to the next page.